Eyewear (sunglasses, goggles, visors, and the like) is employed for reducing glare caused by reflected light from water, road surfaces, snow, and the like. For example, with sunglasses, the lens parts are tinted with pigments or the like so as to reduce the amount of light entering the eyes and reduce glare, through absorption of light by the pigment. Polarized sunglasses are particularly effective against reflected light from water, snow, and the like.
Because reflected light is polarized light, polarized sunglasses are designed to effectively absorb light in the polarization direction thereof, so that glare can be reduced and visibility improved without significantly reducing the amount of light entering the eye.
Polarized sunglasses, which typically have polarizing elements sandwiched by supports of polycarbonate or the like, can be obtained by machining these to the desired shape and fitting them into a frame. The polarizing elements are typically films in which dichromatic dyes, or “dichromatic pigments,” which are polyvalent iodine-polyvinyl alcohol (PVA) complexes, are uniaxially oriented together with polymers such as PVA. Depending on the color of the pigments used, polarizing elements of various colors can be obtained, but normal sunglasses are often tinted gray in order to impart polarizing properties throughout the entire visible light spectrum.
In some cases, multilayer films are vapor-deposited onto surfaces of polarized sunglasses in order to impart design qualities, or further improve visibility. By imparting a multilayer film, reflected light from the sunglass surface can be made to appear to others to have a metallic-tone hue of blue, green, or red, while by reflecting specific light, from the wearer's perspective, glare is reduced, and the visibility of the landscape is further improved. While imparting a multilayer film in this manner is advantageous for the wearer, a problem in terms of handling, specifically, that sebum or the like adhering to a multilayer film is difficult to remove, or a problem of peeling of the multilayer film in locations of exposure to moisture such as seawater or to salt air, was sometimes encountered.
To address this problem, methods such as placing the multilayer film on the inside of the support, i.e., between the polarizing element and the support, have been considered. However, because the reflecting abilities of a multilayer film are produced by differences in refractive index between the layers, it is difficult to obtain reflecting abilities comparable to an interface with the outside air. Moreover, because multilayer films comprise inorganic substances, adhesion to polarizing elements, which are organic, can be a problem.
There are other methods in which, rather than employing a multilayer film, a cholesteric liquid crystal layer is employed as a method for imparting a metallic hue using an organic substance, such as that disclosed in Patent Document 1 (Japanese Laid-Open Patent Application 2001-180200). In cholesteric liquid crystals, the liquid crystal molecules exist in a helically oriented state, and depending on the length of the helical pitch, have the ability to selectively reflect polarized light components having the same direction as the direction of the helix within a specific wavelength band. An optical laminate that employs a cholesteric liquid crystal layer with a fixed helical orientation producing a desired reflection wavelength band will have a vivid hue, and can impart ornamental qualities.